What exactly is included in Blackberry Basic?

I have an add-on called Blackberry Basic ($10/month) on my bill, but I have no clue what that gives me. BBM works fine, but I don't get any social stuff. Am I paying $10 for just BBM even though there's another add-on that allows me to get it for $5?

Thanks so much. One last question:
I can currently use Whatsapp off wifi even though I don't have data (I'm guessing it does it through BIS?), will I still be able to use Whatsapp if I got the BBM add on?